celest

From a set of two-line elements of the ISS (or any low-earth orbit satellite), inspect will calculate the latitude, longitude, altitude, SAA passes and night passes of the ISS. The duration of the prediction as well as the time step is settable by the user.

inspect use the SGP4 library written by D. Vallado in C++ to process the given TLE.

input TLE

inspect can only support the following TLE format (the first line being optional. But if present should be 24 characters long)

ISS (ZARYA)
1 25544U 98067A   18304.35926896  .00001207  00000-0  25703-4 0  9995
2 25544  51.6420  60.1332 0004268 356.0118  61.1534 15.53880871139693

the input file can be read by inspect from a local file or a remote file available on a http/https server.

inspect output

the output of inspect consists of a csv file. The columns of the file are:

• datetime (YYYY-mm-dd HH:MM:SS.ssssss)
• modified julian day
• altitude (kilometer)
• latitude (degree or DMS)
• longitude (degree or DMS)
• eclipse (1: night, 0: day)
• crossing (1: crossing, 0: no crossing)
• TLE epoch (not printed when output is pipe separated)

coordinate systems:

inspect can give the position of a satellite in three different way (mutually exclusive):

• geocentric: the latitude, longitude and altitude are calculated from the centre of the earth.
• geodetic: the latitude, longitude and altitude are calculated above an ellipsoidal surface of the earth.
• teme/eci: the latitude, longitude and altitude are calculated from the centre of the earth. The main difference is that, in this system, the values are computed in an inertial system that do not rotate with the earth. These values are the outcome of the SGP4 propagator used by inspect and are used the computed the latitude, longitude in the geodetic or geocentric system.

usage

$ inspect [options] <file|url>

  -b       DATE    start date
  -c       COORD   coordinate system used (geocentric, geodetic, teme/eci)
  -d       TIME    TIME over which calculate the predicted trajectory
  -f       FORMAT  print predicted trajectory in FORMAT (csv, pipe, json, xml)
  -i       TIME    TIME between two points on the predicted trajectory
  -r       AREA    check if the predicted trajectory crossed the given AREA
  -s       SID     satellite identifier
  -t       DIR     store a TLE fetched from a remote server in DIR
  -w       FILE    write predicted trajectory in FILE (default to stdout)
  -bstar   LIMIT   B-STAR drag coefficient limit
  -360             longitude are given in range of [0:360[ instead of ]-180:180[
  -dms             convert latitude and longitude to DD°MIN'SEC'' format
  -config          load settings from a configuration file
  -version         print inspect version and exit
  -info            print info about the given TLE
  -help            print this message and exit